Glossary
frequency—A characteristic of an electrical or electronic signal which describes the periodic recurrence of cycles. Frequency is inverse ly proportional to the wavelength or pulse width of the signal (e.g., long wavelength signals have low frequencies and short wavelength signals yield high frequencies).
function: A Universal Serial Bus device that provides a capability to the host. For example, an ISDN connection, a digital microphone, or speakers.
H
handshaking—A process that two modems go through at the time of call setup to establish synchronization over the data communications link. It is a synchronization and negotiation process accomplished by the exchange of predefined, mutually recognized control codes.
HDLC (High-Level Data Link Control)—An ISO standard, bit-oriented data communications protocol that provides nearly error-free data transfers.
hexadecimal—A base 16 numbering system in which one character represents a four-bit binary value. Hexadecimal notation uses the numbers 0–9 and the letters A–F, usually suffixed by an h (e.g., 4CF h).
Host Controller: The host’s Universal Serial Bus interface. A hardware device that provides the interface to the Host Controller Driver (HCD) and the USB bus.
Host Controller Driver (HCD): Software that provides an interface to the USB Driver and the Host Controller. (The interface to the Host Controller is defined by the OHCI specification.
I
IDN (Integrated Digital Network)—The culmination of transmission and switching functions using digital technology in a circuit-switched telecommunications network.
IEC (Inter-Exchange Carrier)—A telephone company that is allowed to provide long distance telephone service between LATAs, but not within any one LATA. Also called IXC.
I-mux(inverse multiplexer)—A device that will dial up and combine several lower speed circuits into a virtual broadband circuit. It takes any multiple up to an aggregate bandwidth, giving users bandwidth on demand for videoconferencing, LAN-to-LAN connections, etc. In ISDN devices, inverse multiplexing is performed by the BONDING protocol.
in-bandsignaling—A technique in which connection control information is sent over the same channel as assigned to the subscriber for end-to-end communication. Two common examples are DTMF line signaling and MF trunk signaling.
Internet—A computer network consisting of many millions of university, government, and private users around the world.
Internet address—A unique 32-bit address for a specific TCP/IP host on a network. Normally printed in dotted decimal format (e.g., 129.128.44.227).
I/O address—A location within the I/O address space of your computer used by a device, such as an expansion card, a USB port, or an internal modem. The address is used for communication between software and a device.
IP address—A unique 32-bit address for a specific TCP/IP host on a network. Normally printed in dotted decimal format (e.g., 129.128.44.227).
IRQ (interrupt request)—The notification a processor receives when another portion of the computer’s hardware requires its attenti on. IRQs are numbered so that the device issuing the IRQ can be identified, and so that IRQs can be prioritized.
ISA (Industry Standards Architecture)—Pronounced ice-a. The classic 8- or 16-bit architecture introduced with IBM’s PC-AT computer. Due to speed constraints, IBM later introduced a restructured Micro Channel Architecture with a 32-bit bus and increased addressing capabilities.
ISDN (Integrated Services Digital Network)—International telecommunications standard for transmitting voice, video and data over a d igital communications line.
ITU-T(formerly CCITT)—International Telecommunications Union–Telecommunications Sector; the United Nations organization that prepares standards for resolving communications issues and problems.
